Well i cant make mods, but i recognise the potential of a game i like.
anyhow, would it be possible for any modders to use the stalker engine to make a mod based on john carpenters "the thing", i think this mod would really suit such an idea with its FPS and RPG elements, along with its ability to mod freakish looking monsters, and it would be really awesome anyway.
ummm... that sounds like you want to change the game altogether. i think it would just be best if you went out and bought The Thing for the PS2.
to do such an extensive mod you'd have to wait till the devs release the sdk. i wouldn't think it possible at the current level of modding.
To actually get the feel you're looking for, you'd probably need whole new weapons and monsters. Which is impossible since we can't model anything new.
I'm not really sure how your idea would work, not very many details. There are some major differences... Stalker is spread out over many places. The Thing took place in an Arctic 'base' (Forget what it was.) Stalker has you fight many monsters. The Thing was just one that could change form and adapt to new life forms so it could act like them and fit in to get closer to its enemy.
I could see setting it up in one map, substitute radiation for the cold weather, and just make one really powerful monsters that would need a **** load of AI scripting to make work as an enemy. And setting up the triggers to give you a reason to go outside (IE: Turn the lights on. Seal up a 'bunker' that would be easy to defend, but is current cold [read: bathed in radiation] so you'd have to turn the heat on to use it.) would take quite a bit to do, if not a solid Map Editor.
Doesn't seem like it holds water, sorry.